Device for the variable actuation of gas exchange valves of internal combustion engines and method for operating said device

ABSTRACT

The invention is characterized in that the gas exchange valves of a cylinder are displaced in a displacement unit ( 15, 34 ) jointly and independently of the displacement of the displacement devices of the other cylinders. Every displacement unit ( 15, 34 ) is associated with separate actuators for actuating the same. Angle of rotation sensors ( 42, 43 ) are provided to detect the angle or rotation signals of the crankshaft and the camshaft or any other shaft rotating at half the crankshaft speed. These angle of rotation signals are used to derive the common idle phase of all valves of a cylinder to be jointly adjusted, a control unit ( 44 ) effecting the displacement of every displacement unit ( 15, 34 ) during said common idle phase.

The invention relates to a device for variable actuation of gas exchangevalves of internal combustion engines of the introductory portion ofclaim 1.

Such devices are used to control gas exchange valves in such a way as tomake it possible to operate reciprocating engines without the throttlevalve that would otherwise be necessary.

Such a device is disclosed in DE 101 23 186 A1, for example. In thisdevice, a rotating cam first drives a connecting link, which executes apure oscillating rotary motion and carries a radial cam, which iscomposed of a rest area and a lift area. The radial cam transfers thelifting curve necessary for actuation of the valve to the roller of adriven element similar to a cam follower which in turn actuates thevalve. The desired different valve lifting curves are produced by thefact that the center of rotation of the connecting link is displaced onan arc-shaped path which is concentric to the roller of the drivenelement when it is in the position that it assumes when the valve isclosed. The center of rotation is formed by a roller which is providedon the connecting link and which is supported in a non-positive manneron an arc-shaped track in the housing; this track is also concentric tothe roller of the driven element, that is, it forms an equidistant tothe path of the center of rotation and is designated as the coulisse. Inaddition, the roller on the connecting link is supported against a camdisk, whose angular position determines the position of the center ofrotation on its arc-shaped path.

DE 101 00 173 describes a completely variable valve train which hasdriving means, for example a cam and, arranged between the driving meansand the gas exchange valve, a connecting link, which acts indirectly onthe gas exchange valve; the valve stroke can be changed by adjusting anadjustable guide element.

Other devices of this type have been disclosed in which the center ofrotation of the connecting link driven by the cam is supposed to beadjusted on a circular path (OS 195 32 334 A1; EP 0 717 174 A1; DE 10164 493). However, the previous publications do not contain any teachingabout how to construct the devices to realize such adjustment.

However, the prior art device has some disadvantages. All known deviceshave the common disadvantage that due to manufacturing tolerances themore the valve strokes of the individual cylinders are reduced for thepurpose of controlling the load, the greater their differences relativeto one another. Moreover, the valve strokes of the gas exchange valvesof the same cylinder cannot be changed independently. Completelyshutting off the gas exchange valves, that is keeping them closedconstantly, and the possibility of turning off a cylinder by completelyturning off all intake and/or exhaust valves of individual cylinders,has also not previously been known. Another disadvantage results fromthe fact that the adjustment of the valve lifting curve occurs duringthe valve stroke of at least individual gas exchange valves. Thisrequires a high adjusting force, that is, a high adjustment torque withhigh adjusting power.

It is an object of the invention to create a device which avoids thedisadvantages of the prior art and allows additional variability forvalve actuation that is entirely mechanical.

This accomplished with the distinguishing features of claims 1 or 2.Advantageous embodiments and further developments are described inclaims 2 through 10. Claims 11 and 12 describe processes for operatingthe inventive device. The displacement of the transmission elements,which causes the change in the valve lifting curve, is performed inseparate units for each gas exchange valve or in separate units forseveral gas exchange valves, each of which is adjacent, and this is donein such a way that these units are adjusted independently of oneanother, at least some of the time.

In one embodiment of the invention, the position of the changeabletransmission element on the respective adjustment curve preferably isdetermined by direct or indirect contact with one or more cam disks,which are put on one or more adjusting shafts that are connected in atorsionally rigid manner. In another embodiment, the cam disks are puton an axially displaceable adjusting axle. The adjusting shaft or theadjusting axle can in turn be rotated or displaced through a suitabletransmission or a connecting element by an adjusting motor. Of coursethe adjustment can also be accomplished by hydraulic elements. If theunits are guided by a linearly adjustable slide, the adjustment can alsobe accomplished directly from the adjusting motor through a spindlewhich has a movement thread.

All embodiments also share the fact that the connecting links or theircam rollers have to be held in contact with the cams by special springs.This is immediately seen from the situation at zero lift, when there iscylinder cutout.

The inventive device, including an adjusting motor or an adjustingdevice, can be separately provided for every valve of an engine, so thatany combination of valve strokes or opening angles of the individualvalves of an engine is possible, including the turning off of individualcylinders. However, as a rule common adjustment of several valves isprovided. This applies especially for intake and exhaust valves of acylinder in multiple-valve engines. For example, two intake valves canbe actuated by a cam through a connecting link which has a radial camfor each valve. Since only one connecting link and only one guide of theunits are present, both valves are adjusted together and in the sameway. However, the inventive device also allows the common connectinglink to have two different radial cams on it with the result of twodifferent lifting curves on the two valves, despite the fact that theyare adjusted together. This variant makes it possible, especially in thelowest load range, to open only one of the two valves. The specialadvantage of this possibility is that in the lowest load range it isonly necessary to expose very small cross sections which can be moreprecisely observed, if they are only exposed by one valve. In addition,opening only one of the intake valves makes it possible to produce swirlin the cylinder charge. The inventive device further expands thepossibilities for producing different valve lifting curves for twointake or exhaust valves of a cylinder by the fact that two differentcams and two connecting links are used with different radial cams.Nevertheless, the two valves can be adjusted together, since the twoconnecting links can be mounted on a common unit.

It is also possible to adjust the displacement of transmission elementswhich cause a change in the valve lifting curve of a larger number ofparallel valves together by an adjusting motor or mechanism, especiallywhen it is mounted on a common unit.

Since it is of great significance for the acceptance of variable valveactuation, that is also the inventive device, to keep the adjustingpower small, and since it is higher when the device or its slip jointsand links are in loaded condition than when they are in the load-freestate that is present to a great extent when the valve is closed, theinventive device provides adjustment essentially during the common restphases of all valves to be adjusted in common. These rest phases arederived from the signals of [sensors on] the crankshaft and thecamshaft, and become shorter and shorter the more valves are adjustedtogether. Thus, the number of valves adjusted together is limited.

The common adjustment of the intake and exhaust valves only of onecylinder in every case produces long rest phases that are “friendly” toadjustment. However, it also makes possible individual load control ofthe individual cylinders with an inventive adjustment strategy thatinvolves controlling the torques of the individual cylinders for eachload state of the entire engine. This is essential for enginesmoothness, especially in the lower load range, since manufacturingtolerances mean that the valve strokes do not sufficiently coincide. Thesignals necessary for this adjustment strategy are also supplied by therotational angle sensor of the crankshaft and assigned to the individualcylinders by the rotational angle sensor of the camshaft.

In a variant of the inventive design, the displacement of transmissionelements, which causes the change in the valve lifting curve, isimplemented by means of a common, rotatable adjusting shaft with camdisks. If the adjustment of all or at lease some of the intake andexhaust valves is largely independent, this offers the possibility ofturning off selected valves by means of the continuous adjusting shaft,that is no longer opening them or at least adjusting a smaller valvestroke. To accomplish this, sections of the described cam disks of theadjusting shaft are formed as a rest for the valves that are not turnedoff. The rest area is a contour which is formed from an arc that isconcentric to the center of rotation of the adjusting shaft. Rotation ofthe adjusting shaft does not change the valve stroke of the displacementunits controlled by the cam disks with rest within the active area ofthe rest, while the valve stroke of the displacement units controlled bythe cam disks without rest is changed. This change can be carried outuntil the valve(s) is/are held completely closed. If all intake valvesor/and the exhaust valves of the same cylinder are triggered in thisway, the change in load is turned off for selected cylinders. Of coursethe same function is achieved by using a straight guided draw key with acorresponding cam contour. The rest area is then a contour which isformed from a line parallel to the sliding direction of the draw key.

The invention is explained in greater detail below by means of drawingsof a few sample embodiments. In the associated drawings,

FIG. 1 shows the moving parts of the generic device, which are involvedin the flow of force from the camshaft to the valve;

FIG. 2 shows a cross-section using the parts shown in FIG. 1 with apendulum support and adjusting shaft,

FIG. 3 is a cross-section through the device with a slide, adjustingshaft, and adjusting motor;

FIG. 4 is a perspective view of the inventive device with a slide andadjusting shafts in an inline 4 cylinder engine;

FIG. 5 is a diagrammatic representation of the interaction of the enginemanagement system, the gas pedal, the rotational angle sensor, adjustingmotors, and battery and

FIG. 6 is a diagrammatic representation of a continuous adjusting shaftand a section through each of two cam disks for positioning a cylinder'sdisplacement unit.

FIG. 1 shows a camshaft 1, which has a cam 2. The cam moves roller 3 atthe end of connecting link 4. Connecting link 4 has a radial cam 5 whichis composed of a rest area 5 a and a lift area 5 b. Connecting link 4 ismounted on a bolt 6 whose axis 7 is guided on an arc-shaped adjustmentcurve 8. The center of the arc-shaped adjustment curve 8 is on the axis9 of the roller 10 of the driven element 11 which is supported through alink 12 in a housing (not shown) and actuates valve 13. It can clearlybe seen that adjustment of axis 7 on the adjustment curve 8 in thedirection of arrow 14 has the consequence of reducing the opening angleand stroke of valve 13.

FIG. 2 shows an embodiment in which the bolt 6 or its axis 7 is guidedon the arc-shaped adjustment curve 8 by form-fit connection to apendulum support 15. Cylinder head-side link 16 of pendulum support 15or its axis coincides with the axis 9 of roller 10 of driven element 11.Adjusting shaft 17 holds cam disks 18, which determine, through tappet18 a, the position of bolt 6 or its axis 7 on the adjustment curve 8.Axis 7 is adjusted on adjustment curve 8, as shown by arrow 14, byrotation of cam disk 18 or adjusting shaft 17 in the direction arrow 14a. The described adjustment movement has the consequence of reducing thestroke and opening angle of valve 13.

FIG. 3 shows a cross-section through an embodiment of the inventionusing a slide 34, which can be used separately for each valve or eachpair of valves. The separate use for individual valves results in thelongest possible rest phases or common rest phases, so that it is easyfor the adjustment to be done only during the rest phases. Controllingthe individual cylinders using the inventive device even requires theseparate arrangement. In this embodiment, bolt 6 is guided in a form-fitmanner in the housing by slide 34, so that its axis 7 is guided alongadjustment curve 35, a line. This line is a tangent and only more orless approximates an arc about the axis 9 of roller 10 of the restingdriven element 11. The deviation is exaggerated in FIG. 3. Now if thethreaded spindle 36 driven by adjusting motor 23 rotates and displacestoothed rack 37 by the amount shown by arrow 38 a, then adjusting shaft17 and cam disk 18 rotate according to arrow 38 b and slide 34 alongwith bolt 6 are displaced by amount 38 c. Because of the deviation ofstraight adjustment curve 35 from the shape of an arc, play compensationelement 31 must be lowered by a certain amount, which is shown by arrow38 d.

FIG. 4 is a perspective view of the inventive device with a slide 34which is separate for each pair of valves of a cylinder. In thisembodiment, slide 34 guides bolt 6 in a form-fit manner in the valvetrain housing (not shown), so that its axis 7 is guided along theadjustment curve 35, a straight line. This line is only more or lessapproximately an arc about the axis 9 of roller 10 of the resting drivenelement 11. Because of the deviation of the straight adjustment curve 35from the shape of an arc, play compensation element 31 must take up acertain amount. Axis 7 is adjusted on adjustment curve 35 by rotation ofcam disk 18 or adjusting shaft 17. The figure shows that in eachcylinder a pair of valves is actuated by means of a cam 2 and aconnecting link 4, which is mounted in a slide 34 on a bolt 6, whoseposition in the valve train housing is guided along an adjustment curve35 in a form-fit manner, and is positioned by means of an adjustingshaft 17 through cam disks 18. If the adjusting shaft 17 of a cylindershould now rotate, then the position of this cylinder's slide 34, andthus the valve lifting curve of both of this cylinder's valves, ischanged. The relationships for the other cylinders do not change. Hereit would also be possible, as is shown later in FIG. 6, for a commonadjusting shaft to position the displacement units of a cylinder groupor a cylinder head.

FIG. 5 is a diagrammatic representation of the interaction of gas pedal40, adjusting motors 23, rotational angle sensor 42 on the flywheel, androtational angle sensor 43 on the camshaft with the engine managementsystem 44. A signal coming from gas pedal 40, that is from a sensor forits position, is converted by engine management system 44 into a signalto adjusting motors 23 to increase or reduce the valve strokes. Afterthe desired load state is achieved for the entire engine, the enginemanagement system 44 evaluates the signals from the high-resolutionrotational angle sensor 42 on the flywheel. They are assigned to theindividual cylinders with the help of the low-resolution rotationalangle sensors 43 on the camshaft or on another shaft running at half thecrankshaft speed. This information is used to send signals to theindividual adjusting motors 23 to even out the torque peaks or thecrankshaft speed, by correcting the valve strokes of the cylinders withsmaller torques upward and correcting those of the cylinders with largertorques downward. In the inventive process an adjustment takes place,with or without compensation, during the common rest phases of thevalves operated by an adjusting motor. The engine management system 44takes their phase positions from sensor 43 of the camshaft.

FIG. 6 is a diagrammatic representation of a continuous adjusting shaft45 of an inline 6-cylinder engine, as well as a section through one oftwo cam disks for positioning a cylinder's displacement unit. Theadjusting shaft carries cam disks 46, 47 for positioning thedisplacement units for the six cylinders. Each of the cam disks 46 forcylinders # 1, #4, and #5, as well as cam disks 47 for cylinders #2, #3,and #6 are the same. AA shows a cross section through the cam disks 46,and BB shows a cross section through cam disks 47. Sector R of cam disk47 is formed by an arc 49 that is concentric to the center of rotation48 of adjusting shaft 45, while in the corresponding sector of cam disk46 the adjusting cam curve continuously leads to a smaller distance tothe center of rotation 48. Such a design of cam disks 46 and 47 has theresult that when adjusting shaft 45 is rotated about its center ofrotation 48, the displacement units for the valves of cylinders #1, #4,and #5 are further displaced in the active area of sector R, while thedisplacement units for the valves of cylinders #2, #3, and #6 remain atrest. In this way, a corresponding design of the valve train can, forexample, keep the valves of cylinders #1, #4, and #5 constantly closedin the adjacent active area of sector N, while the valves of cylinders#2, #3, and #6 still execute a stroke.

LIST OF REFERENCE NUMBERS

-   1 Camshaft-   2 Cam-   3 Roller-   4 Connecting link-   5 Radial cam-   5 a Rest area-   5 b Lift area-   6 Bolt-   7 Axis-   8 Adjustment curve-   9 Axis-   10 Roller-   11 Driven element-   12 Link-   13 Valve-   14 Arrow-   14 a Direction arrow-   15 Displacement unit-   16 Link-   17 Adjusting shaft-   18 Cam disk-   18 a Tappet-   19 Intake valve-   20 Exhaust valve-   21 Sliding block-   22 Articulated shaft-   23 Adjusting motor-   31 Play compensation element-   34 Slide, displacement unit-   35 Adjustment curve-   36 Threaded spindle-   37 Toothed rack-   38 a Arrow-   38 b Arrow-   38 c Amount-   38 d Arrow-   40 Gas pedal-   42 Rotational angle sensor-   43 Rotational angle sensor-   44 Engine management system, control unit-   45 Adjusting shaft-   46 Cam disk-   47 Cam disk-   48 Center of rotation-   #1 Cylinder-   #2 Cylinder-   #3 Cylinder-   #4 Cylinder-   #5 Cylinder-   #6 Cylinder-   R Sector

N Sector Key for Figures Batterie Battery Drehwinkelsensor Rotationalangle sensor Fahrpedal Gas pedal Figur Figure Kurbeiwelle CrankshaflMotormanagement Engine management system Nockenwelle Camshaft Schwungradmit Drehwinkelsensor Flywheel with rotational angle sensorVersteilmotoren Adjusting motors

1. Device for variable actuation of gas exchange valves of internal combustion engines with several cylinders, in which (one or) more cams (2) of a camshaft (1) mounted in a housing rotate as a function of the engine speed, with a connecting link (4), which can be actuated by this or these cam(s) (2) through a first curved link and with a driven element (11) which transfers the motion to the gas exchange valve (13) and which is connected with the connecting link (4) directly or through other connecting links, and, between one of the connecting links (4) and the driven element (11), with at least one other curved link which has a section (5 a) in which no lifting motion for the gas exchange valve (13) is transferred through the driven element (11) and has another section (5 b) in which a lifting motion for the gas exchange valve (13) is transferred through the driven element (11), and with the capability of displacing at least one of the transmission elements along a displacement path (8, 35) and, in so doing, modifying the course of the lifting curve of the gas exchange valves, characterized in the gas exchange valves of one cylinder in a displacement unit (15, 34) are displaced together with and independently of the displacement units of the other cylinder, each displacement unit (15, 34) being assigned separate actuators to operate it, that rotational angle sensors (42, 43) are provided to capture rotational angle signals of the crankshaft and the camshaft or another shaft running at half the crankshaft speed, from which it is possible to derive the common resting phase of all valves of a cylinder to be adjusted in common, and that a control unit (44) is present which causes the displacement of each displacement unit (15, 34) essentially during this common resting phase.
 2. Device for variable actuation of gas exchange valves of internal combustion engines with several cylinders, in which (one or) more cams (2) of a camshaft (1) mounted in a housing rotate as a function of the engine speed, with a connecting link (4), which can be actuated by this or these cam(s) (2) through a first curved link and with a driven element (11) which transfers the motion to the gas exchange valve (13) and which is connected with the connecting link (4) directly or through other connecting links, and, between one of the connecting links (4) and the driven element (11), with at least one other curved link which has a section (5 a) in which no lifting motion for the gas exchange valve (13) is transferred through the driven element (11) and which has another section (5 b) in which a lifting motion for the gas exchange valve (13) is transferred through the driven element (11), and with the capability of displacing at least one of the transmission elements along a displacement path (8, 35) and, in so doing, modifying the course of the lifting curve of the gas exchange valves, characterized in that at least one displacement unit (15, 34) is present which carries out the displacement to affect the lifting motion of at least one gas exchange valve (13) independently of the displacement of other displacement units to affect lifting motion of other gas exchange valves (13); a common adjusting shaft (45) is provided which can, for a number of gas exchange valves (13), directly or indirectly adjust, by means of at least one cam disk (46 or 47) per displacement unit, the respective required position of the transmission elements, which can be displaced along the displacement path (8, 35), on this displacement path (8, 35), and these transmission elements can be supported essentially in the direction of displacement; the cam disk (47) for at least one displacement unit has a section (49) made as a rest which causes no change in the position of the transmission elements guided on the displacement path (8, 35) when the adjusting shaft (45) is rotated; and the cam disk (46) of at least one other displacement unit (15, 34) has a corresponding section without a rest which does cause a change in the position of the transmission elements guided on the displacement path (8, 35) when the adjusting shaft (45) is rotated.
 3. Device of claim 2, characterized in that the section without rest of the cam disk (46) has a sector R in which the contour curve (adjusting cam curve) continuously leads to a smaller distance to the center of rotation (48) of the adjusting shaft (45).
 4. Device of claim 3, characterized in that the contour of cam disk (46) has a sector N arranged adjacent to sector R, in which the contour curve (adjusting cam curve) is such that the valves of the cylinder which are actuated when this sector N becomes active remain constantly closed, while the contour of cam disk (47) has a corresponding sector N in which the contour curve is such that the valves of the cylinder which are actuated when this corresponding sector N becomes active still execute a lift.
 5. Device of claims 2, characterized in that adjusting shaft (45) has several identical cam disks (46) and several identical cam disks (47) arranged on it, and each of the cam disks (46) and (47) are oriented so that they have the same angular position to one another, i.e., they not rotated with respect to one another.
 6. Device of claims 1, characterized in that two identical cams and two connecting links with identical radial cams are used for the two valves of a cylinder.
 7. Device of claims 1, characterized in that two different cams and two connecting links with different radial cams are used for the two valves of a cylinder.
 8. Device of claims 1, characterized in that two identical cams and two connecting links with different radial cams are used for the two valves of a cylinder.
 9. Device of claims 1, characterized in that two different cams and two connecting links with identical radial cams are used for the two valves of a cylinder.
 10. Device of claims 1, characterized in that a common connecting link is used with two identical radial cams for the intake or exhaust valves of a cylinder.
 11. Device of claims 1, characterized in that a common connecting link is used with two different radial cams for the valves.
 12. Device of one or more of claims 1, characterized in that at least one valve is adjusted all the way, so that it is closed constantly.
 13. Device of one or more of claims 1, characterized in that all intake or exhaust valves of a cylinder are combined in a displacement unit (15, 34).
 14. Process for operating an internal combustion engine with several cylinders using one or more devices of one or more of claims 1, characterized in that after a desired load state for the entire engine is reached a) angular position signals of the crankshaft are picked up with a first rotational angle sensor (42) on the flywheel and evaluated by an engine management system (44) in order to detect rotational irregularities of the crankshaft and/or torque peaks; b) these are assigned to the individual cylinders with the help of a second rotational angle sensor (43) arranged on the camshaft or on another shaft running at half the crankshaft speed; and c) this information is used to produce signals which go to drives for the individual displacement units to even out the torque peaks and/or the crankshaft speed, by correcting the valve strokes of the cylinders with the smaller torques upward and correcting those of the cylinders with the larger torques downward.
 15. Process for operating an internal combustion engine with several cylinders using one or more devices of one or more of claims 1, characterized in that a) each cylinder has assigned to it a separate device and an actuator to operate the device; b) the phase position of the rest phases of the individual valves operated by an actuator is determined; and c) the adjustment movements of the respective devices take place essentially during the common rest phases of the valves operated by the respective displacement unit.
 16. Process of claim 15, characterized in that the phase position of the rest phases of the individual valves is determined by an engine management system (44) from the signal of a rotational angle sensor (43) arranged on the camshaft. 